Amplifier power supply



July 1, 194 P. c. GARDINER AMPLIFIER POWER SUPPLY Filed July 12, 1940 miN r v :e W PM n d P a .t t; M .5

m H Hm Patented July 1, 1941 Paul C. Gardiner, Scotia, N. Y., assignorto General Electric Company, a corporation of New York Application July12, 1940, Serial No. 345,152

Claims.

This invention relates to amplifiers and more particularly to high gainmulti-stage amplifiers having a common source of operating power.

In providing multi-stage amplifiers with operating power from a commonsource it is necessary to provide signal current filters between thesource and each amplifier stage to prevent intercoupling between thestages which might result in undesirable efiects, such as oscillationand distortion. It is an object of my invention to provide a simpler andcheaper filter system.

between a multi-stage amplifier and a common source of operating powertherefor, which filter at the same time minimizes intercoupling betweenstages of the amplifier.

It is a further object of my invention to provide filters connectedbetween a multi-stage amplifier and a common source of power therefor,such that the filtering action between the first and last stage of suchan amplifier is substantially as effective as between adjacent stages,no matter how many stages the amplifier may contain.

The features of my invention which I believe to be novel are set forthwith particularity in the appended claims. My invention itself, however,both as toits organization and method of operation, together withfurther objects and advantages thereof maybest be understood byreference to the following description taken in connection with theaccompanying drawing in which the single figure of the drawingrepresents a preferred embodiment of my invention.

In thefigure a six-stage amplifier is illustrated, which hasrespectively six electron discharge devices H], H, t2, is, M and I5, onein each stage. These stages are suitably coupled, as illustrated, byinductively coupled circuits provided between the output of each ofthese devices and the input of the succeeding device. Tuned outputcircuits for the devices Iii through I5 are respectively circuits l6,ll, l3, I9, and 2|.

A common source 22 of operating power is provided for the multi-stageamplifier comprising devices Hi through l5 inclusive. This power sourceis illustrated as of a conventional type of power supply and need not bedescribed in detail. It is energized from a source of alternatingcurrent mains power, and produces :a continuous potential between groundand a conductor 23.

The electron discharge devices [3 through [5 are supplied respectivelywith operating power connected: from a-point between resistors 24 and 25to ground. A third by-pass condenser 28 is connected from a pointbetween resistor 25 and tuned output circuit I8 to ground. The resistors24, 25 and the condensers 26, 21 and 28 constitute two cascade-connectedfilters between the source 22 and the output circuit l8.

A similar circuit supplies power for device I3 and extends fromconductor 23 through a resistor 29, resistor 30, tuned output circuitI3, device it, ground, and thus back to the source 22. A by-passcondenser 3| is connected from a point between resistors 29 and 30 toground and a second by-pass condenser 32 is connected from a pointbetween the resistor 39 and the output circuit I9 to ground. Theresistors 29 and 33-- with their associated condensers 25, 3| and 32therefore form two cascaded filters between the source 22 and the outputcircuit It.

A power circuit for the device ll extends from the source 22 throughconductors 23, resistors 24, 33 and 34, circuit [1, devic It to ground,and thus back to the source 22. A by-pass condenser 35 is connectedfroma point between resist0rs,33' and 34 toground. A second by-passcondenser 36 is connected from a point between resistor 34' and outputcircuit IT to ground.

A similar power circuit for the device H extends from the source 22through the conductor 23, resistors 29, 31 and 38, output circuit 20,device M' to ground, and back to the source 22. A by-pass condenser 39is connected from a point between resistors 31 and 38 to ground and asecond condenser 40 is connected from a point between resistance 38 andoutput circuit 20 to ground. Therefore between each of the devices I Iand N there are three cascaded filters between the source 22 and theoutputcircuit associated with the respective discharge device.

The variousfilters are illustrated as being connected in cascade ratherthan as being individually connected from the output circuit for eachdischarge device to the source 22, as is the usual case. Such cascadeconnection provides that much higher attenuation exists for signalcurrent passing between two remote discharge devices'through the power spply circuit than for signal current passing between two adjacentdevices in which the signal levels are more nearly equal. For examplethe signal level is nearly equal in the devices I3 and I4, which havethree filters connected in cascade therebetween in their power supplycircuit. -On the other hand, the signal levels in the devices II and Mare widely different. The level in the device I 4 is much higher thanthe signal level in the-device II.

There are six cascaded filters in the power circuit between these tworemote devices, and these six filter sections provide a high degree ofattenuation for signal current passing through the power circuit betweendevices II and I4.

A power circuit for the device I!) extends from the source 22 throughthe conductor 23, through resistors 24, 33, 4| and 42, to the outputcircuit I6, and thence through the device H) to ground and back to thesource 22. A by-pass condenser 43 is connected from a point between theresistors 4| and 42 to ground, and a second by-pass condenser 44 isconnected from a point between resistor 42 and output circuit 16 toground.

A power circuit for the device l5 passes from the source 22 through theconductor 23 and through resistors 29 and 31, through a pair ofresistors 45 and 46 in series, through the output circuit 2! and throughthe device I5 to ground and back to the source 22. A condenser 41 isconnected from a point between resistors'45 and 46 to ground and asecond condenser 48 is connected from a point between resistor 46 andoutput circuit 2! to ground. The devices In and I5 therefore each havefour filter sections between their corresponding output circuits and thesource 22 with correspondingly high attenuation of signal currents.

Care must be exercised in connecting power supply circuits of thisnature that the source 22 be connected to approximately the centralpoint of the cascaded resistors 42, 4|, 33, 24, 29, 31, 45 and 46, whichare connected serially from the first discharge device It] to the lastdischarge device Hi.

In case the multi-stage amplifier includes an even number of dischargedevices, as illustrated, it is preferred to provide, as shown, a pair ofresistors between the central pair of discharge devices and to connectthe source of power between these two resistors. In the circuitillustrated, two such resistors 24 and 29 have been provided, betweenwhich the conductor 23 from the source 22 is connected. If themulti-stage amplifier should have an odd number of discharge devices,the source of power may be connected to a point of the cascaded filtersnearest to the central discharge device in the amplifier.

When the source 22 is centrally connected to the cascaded power supplyfilters, along which the discharge devices are connected, any couplingwhich may exist between the output of discharge devices transmittingrelatively powerful signals and the input of devices carrying weaksignals produces substantially no undesirable reaction. If the source 22were connected to one end of the cascade-connected power supply filtersnearest the discharge device IS, the high level signal at the device 15would be radiated from circuits of the source 22 in spite of attenuationin filters between the source 22 and the output circuit 2!. Thisradiation from the relatively large surfaces of the source 22 isproportionately strong in relation to signal current in signal circuitsassociated with the device H], which would therefore pick up theradiation and tend to produce oscillation or distortion through theamplifier.

If, on the other hand, the source 22 were connectedto that end of thecascaded power supply filters near the device H], the large surfaces ofthe source 22 would pick up radiation of high level signals in thecircuits associated with the device 15. This radiation, picked up by thelarge surfaces of the source 22, would be transmitted through filtersbetween the source 22 and the output circuit [6 in sumcient strength toaffect the relatively weak signals passing through the device I!) andproduce distortion or even oscillation. By providing for connection ofthe source 22 near the center of the cascade-connected -power supplyfilters, the effect of such radiation is minimized and simpler andcheaper filters may be used.

While I have shown a particular embodiment of my invention, it will, ofcourse, be understood that I do not wish to be limited thereto, sincedifferent modifications may be made both in the circuit arrangement andinstrumentalities employed, and I aim by the appended claims to coverany such modifications as fall within the true spirit and scope of myinvention. What I claim as new and desire to secure by Letters Patent ofthe United States is:

1. A multi-stage amplifier having at least three cascade-connectedelectron discharge devices and a common source of power therefor, apower supply filter connected between each pair of adjacent dischargedevices, said filters being connected in cascade with each other, and aconnection from said source of power to an intermediate point along saidcascade-connected filters to supply power to said devices.

2. An amplifier having more than two cascadeconnected electron dischargedevices, a plurality of corresponding cascade-connected power supplyfilters and a common source of powerfor said devices connected to anintermediate point on said filters, and means connected between eachpair of adjacent cascade-connected filters to supply power to therespective cascade-connected electron discharge device.

3. In combination with at least three cascaded signal amplifying stages,a power supply filter connected between each pair of adjacent stages toprovide signal attenuation therethrough between said stages,'saidfilters being connected in cascade with each other to provideprogressively greater signal attenuation through said filters betweenremote signal amplifying stages, a source of operating power for saidstages, and means connecting said source to the central point of saidcascaded filters to produce a minimum of signal coupling between saidstages.

4. An amplifier having more than two cascadeconnected electrondischargedevices, a plurality of cascade-connected filters and a common source ofoperating potential for said devices connected to an intermediate pointon said filters, and means connected between each pair of adjacentcascade-connected filters to supply operating potential to therespective cascade-connected electron discharge device.

5. An amplifier having at least three cascadeconnected electrondischarge devices, a circuit associated with each of said devicesrequiring operating potential, a plurality of cascade-connectedresistances, one of said resistances being connected between each pairof adjacent circuits, a icy-passing condenser connected from thejunction of each pair of adjacent resistances to ground, saidresistances and condensers forming cascaded filters, and a source ofoperating potential for said devices having one terminal connected toground and another terminal connected to an intermediate point of theresistances in said cascaded filters.

PAUL C. GARDINER.

